WO2000002176A1

WO2000002176A1 - Device for improving the security of aircraft in visual flight regime

Info

Publication number: WO2000002176A1
Application number: PCT/FR1999/001594
Authority: WO
Inventors: Claude Le Tallec; Boris Gravier
Original assignee: Onera (Office National D'etudes Et De Recherches Aerospatiales)
Priority date: 1998-07-06
Filing date: 1999-07-02
Publication date: 2000-01-13
Also published as: FR2780701B1; CA2337264C; EP1095362A1; DE69903169D1; US6438492B1; FR2780701A1; EP1095362B1; DE69903169T2; CA2337264A1; ATE225069T1

Abstract

Measurements of the aircraft (10) instantaneous position and speed are included in co-operation messages regularly broadcast by radio to other aircraft (10'). The device wherewith the aircraft, operating in visual flight, is equipped, analyses the data contained in the co-operation messages which it receives from other aircraft and its own trajectory to identify possible risks of collision. Said possible risks of collision are signalled to the pilot, advantageously in voice form, in the messages identifying the direction wherein the other aircraft is visible and estimate of the time lapse remaining until possible collision occurs.

Description

DEVICE FOR IMPROVING THE SAFETY OF AIRCRAFT IN SIGHT FLIGHT REGIME

The present invention relates to a device intended to prevent the risks of collision between aircraft operating in visual flight regime, or VFR (Visual Flight Rul s).

The present invention is adapted to the piloting rules used by VFR pilots, the basic principle of which is: see and be seen. The reason most widely mentioned in crash accident reports is the pilot's inability to see the other aircraft in time. It is therefore desirable to improve the safety of all aircraft under VFR without risking modifying the rules, patterns and habits of pilots flying in VFR.

For this, it is important to take into account the aeronautical constraints specific to VFR light aviation. In particular, the most penalizing constraints are linked to gliders for which: • the available energy is limited to the use of an additional 12 V / 6 A battery;

• the space available is of the order of a few cubic decimetres;

• the maximum mass per square centimeter as well as the total mass are limited to remain within the certification constraints;

• 1 * adding external antennas to the fuselage is unacceptable, as is any modification to the aerodynamics of the machine. A system satisfying these constraints will generally be suitable for all other categories of aircraft flying in VFR, in particular light aircraft, helicopters, ULMs, etc.

Currently, there are numerous anti-collision devices, cooperative or autonomous, applied to aeronautics. - - There are two known categories of autonomous devices:

1) Passive devices, generally optical of the infrared sensor type, are effective for military applications, in which the targets have suitable infrared signatures.

2) Active devices, of the airborne radar type, require the transmission and reception of a radar wave. The signal bandwidth sets the distance resolution performance. Other criteria, such as wavelength, condition the size of the transmit and receive antennas. We can cite five categories among cooperative devices: 1) Certain devices seek to increase the visibility of aircraft (anti-collision lights, bands of colors painted or glued to gliders, ...). These devices are generally dependent on the type of aircraft on which they are installed. They do not significantly increase the pilot's ability to look at the right place in time.

2) Other devices aim to detect the flashes of aircraft anti-collision lights optically. However, these lights are not available on all VFR aircraft. On the other hand, the range of these devices is reduced (of the order of 1 km), which seems insufficient taking into account the typical speeds of light aircraft and the average reaction times.

3) TCAS (Traffic alert and Collision Avoidance Systems) type systems require a large source of energy, and the installation of two sets of transmit and receive antennas respectively on the upper and lower parts of the 'aircraft. They work like a real secondary radar on board. They can only detect aircraft equipped with transponders in operation, which is often not the case with VFR aircraft. Some of these systems use tracking algorithms to provide pilots with avoidance maneuvers. In particular, TCAS II has become compulsory in the USA. for all aircraft with more than 30 seats since 1993.

4) Variants to TCAS require the support of secondary air traffic control radars to listen to the transponders of neighboring aircraft when they are interrogated. This support by secondary radars is not available worldwide, and makes the system dependent on ground installations.

5) Radioelectric devices of the beacon type may include a position determination means, a data transmitter and receiver, a member for calculating potential conflicts, and a display device intended for the pilot. An example of such a device is described in US-A-

4,835,537. Like TCAS, these devices appear to be ill-suited to VFR flight conditions, in that they use display screens on which relatively complex information is presented, some of which relate to aircraft which represent practically no risk. collision.

The pilot's attention is partly captured by the instrument, which is in contradiction with the very principle of visual flight rules.

There is therefore currently no collision prevention device specially adapted to cover the specificities related to the safety of all types of aircraft flying in VFR. In particular, no device makes it possible to take into account complex trajectories, such as those of gliders evolving in evenings ascending, which cause a significant number of accidents.

The invention aims to propose anti-collision devices of the cooperative type which are particularly well suited to VFR conditions.

The invention thus proposes a device for assisting piloting in visual flight, to be installed on board an aircraft, comprising:

- measuring means for estimating at least the instantaneous position and the speed vector of the aircraft;

a radio transmitter / receiver for broadcasting cooperation messages containing parameters representing at least the estimated instantaneous position and speed vector of the aircraft, and for receiving similar cooperation messages broadcast from other aircraft;

means of analysis of the cooperation messages received by the radio transmitter / receiver and of the data coming from the measurement means, in order to identify possible risks of collision with other aircraft; and

a man-machine interface for signaling to the pilot of the aircraft the possible risks of collision identified by the analysis means.

According to the invention, the analysis means are arranged to carry out the following operations at successive analysis instants:

- subdivide an analysis period, starting at the current analysis instant, into a series of consecutive time intervals; - For each of these time intervals, determine a protection volume on the basis of different possible future positions of the aircraft deduced from the data from the measurement means;

- extrapolate the trajectory of each other aircraft, from which a cooperation message is received, on the basis of the parameters contained in this cooperation message, so as to estimate possible positions from that other aircraft during the time intervals in the series; and

- if a condition is fulfilled that an estimated possible position of another aircraft during one of the time intervals in the series is within the protection volume determined for said time interval, order the man interface -machine so that a signaling message indicating the direction in which said other aircraft is at the current analysis time is delivered to the pilot.

Of the cooperative type, the device is common to all aircraft flying in VFR regime, including gliders in particular, and operates a priori with global coverage without the constraints linked to possible control bodies or dependent on ground installations.

The device can operate with a precision allowing to respect the average reaction time of a VFR pilot. This time has been evaluated, according to some studies, at 12.5 seconds between the moment the pilot sees the other aircraft and the moment he avoids it, including the vision of the object (0.1 s), its recognition (1 s), collision certainty (5 s), decision to turn (4 s), muscular reaction (0.4 s), and the average response time of a light aircraft or glider (2 s) ).

The nature and the functioning of the device make it possible not to modify the rules, customs and habits of pilots flying in VFR nor to impose on them a work overload. Preferably, the signaling message also indicates the time remaining until the first of the time intervals of the analysis period for which said condition is fulfilled. This allows the pilot to appreciate the urgency of his intervention. To facilitate visual identification of the other aircraft, the signaling messages advantageously include an indication of apparent size of the third-party aircraft, determined on the basis of actual size indications included in the cooperation messages and of the distance between the two aircraft.

Preferably, the man-machine interface comprises means for delivering the signaling messages in the form of voice messages. In this case, the device does not divert the pilot's visual attention towards the interior of the cockpit, unlike most collision avoidance systems for light aviation which use a display screen to give the pilot a graphic representation of the nearby traffic and / or conflicting aircraft. The structure of the signaling voice message can respond to a specific phraseology comparable to conventional radiotelephone messages, for example: "Traffic, 15 seconds, 11 hours, 10 °, size 2". Thus, the pilot accustomed to receiving such information messages will quickly be able to spot the aircraft presenting a potential danger. He will then make the right decisions to avoid the collision given the situation.

The optimal avoidance maneuver, chosen thanks to the information provided by the device, will be left to the pilot's discretion, in accordance with the VFR regulations which he must apply. Thus, the basis of visual flight rules, which is based on an observation of the surrounding space for 90% of the time, is respected.

The nature of the device and the algorithm used to process the information available allow a good adaptation to the different categories of aircraft envisaged, taking into account their speed, their type of evolution, their average density of distribution, space. available, as well as energy sources usable on board.

In a preferred embodiment of the device, the measurement means are arranged to estimate the instantaneous turning radius of the aircraft in a horizontal plane, on which depend the possible future positions of the aircraft on the basis of which the analysis means determine the protection volumes. By thus adapting the relevant protection volumes to the radius of this instantaneous turn of the aircraft, the effective risks of collision are better taken into account.

The duration of the analysis period is advantageously chosen as an increasing function of the instantaneous turning radius if this is estimated by the measurement means, for example as the minimum between a reference duration (or maximum notice period) and a duration proportional to the ratio between the instantaneous turning radius estimated by the measuring means and the module of the projection on the horizontal plane of the instantaneous speed vector estimated by the measuring means. This makes it possible to limit the information delivered to the pilot who is negotiating a turn, so as not to distract his attention, by avoiding signaling aircraft too far away to represent a real risk of collision taking into account the instantaneous speed and turning radius. This advantage is particularly interesting in the case of gliders which, when they are in an upward spiral, have a tight turning radius and are often surrounded by other gliders which should be pointed out wisely. The device is preferably adjustable by the pilot with regard to the maximum notice period of the danger of collision. This offers him additional comfort corresponding to the reaction time that he will prefer to give himself according to his personal capacities, the average amount of information that he wishes to be delivered and the current flight sentence (takeoff, cruise, approach ...).

The nature of the device allows relatively simple production and inexpensive manufacturing. It can therefore be systematically installed by the owners of small aircraft, unlike some other relatively expensive devices. The wide dissemination of this device, a condition for greater flight safety to be ensured, can therefore be satisfied.

Other features and advantages of the present invention will appear in the following description of nonlimiting exemplary embodiments, with reference to the appended drawings, in which:

- Figure 1 is an illustration of examples of signaling messages delivered by a device according to the invention to pilots of aircraft in VFR regime;

- Figure 2 is an overall diagram of a device according to the invention;

- Figure 3 is a flowchart of operations performed by an analysis module of the device of Figure 2;

- Figure 4 is a perspective view of an elementary protection volume defined around the aircraft; and

- Figures 5 to 7 are schematic elevational views from above and in perspective of a defined protection volume for a given time interval.

Figure 1 illustrates the conditions of application of the present invention, showing two aircraft 10,10 'flying close to each other in visual flight. Each of the aircraft is equipped with a device according to the invention, described in more detail below, which allows its pilot to be delivered, in the form of voice messages, information facilitating the visual identification of the other aircraft if a collision is likely to occur with it in a certain zone Z. Such a voice signaling message is delivered in a form similar to what a co-pilot might say, in order to facilitate its interpretation by the pilot. In the illustration of FIG. 1, this information is made up of five elements: - the first ("Traffic") indicates to the pilot the nature of the message, to draw his attention to the fact that he should be viewing another aircraft; - the second ("20 seconds") provides an estimate of the time remaining until the possible collision in zone Z;

- the third and fourth elements ("3 hours, site plus 5" for aircraft 10, "11 hours, site minus 5" for aircraft 10 ') indicate, in a coordinate system linked to the aircraft, the general direction in which the pilot should look to locate the other aircraft, that is, the direction corresponding to the dashed line in Figure 1. This direction is indicated using an azimuth angle φ expressed, as is usual, in the form of the hour indicated by the small hand of a clock face, and of an angle of elevation expressed in degrees relative to the horizon line; - The fifth element ("size 1") is an indication of the apparent size of the other aircraft, to facilitate its location.

For the development of such signaling messages, each aircraft 10 is equipped with a device comprising:

measurement means for estimating instantaneous parameters x, y, z, V _{χ /} V _y , v _z , R of the trajectory of the aircraft 10 provided with the device, in a coordinate system common to all the aircraft; a radio transmitter / receiver for broadcasting cooperation messages including some of the instantaneous parameters estimated for the aircraft 10, and for receiving similar cooperation messages broadcast by other aircraft 10 ′ located within range of the aircraft 10; means of analysis of the risks of collision on the basis of the trajectory parameters estimated for the aircraft 10 and of the trajectory parameters obtained in the cooperation messages received by the radio transmitter / receiver; - a man-machine interface for delivering signaling messages based on the result of the collision risk analysis. In the device shown in FIG. 2, the measurement means pick up positioning reference signals from a constellation of satellites, such as GPS ("Global Positiomng System") signals. They include a GPS antenna 12 and an associated receiver 13 for processing the GPS signals and deducing therefrom the instantaneous position of the aircraft 10 in the form of its three coordinates x, y, z in a reference independent of the aircraft. For example, the x coordinate can correspond to longitude, the y coordinate to latitude, and the z coordinate to altitude, the xOy plane corresponding to the horizontal plane. For certain parameters, the GPS measurements could be supplemented by measurements carried out by sensors on board the aircraft (for example by an altimeter for the parameter z).

In the architecture shown in FIG. 2, the device comprises a computer 15, such as a microprocessor associated with a working memory and with a program memory. In the block diagram of FIG. 2, the computer 15 comprises three modules 16,17,18 which, in practice, can be software modules, that is to say program elements executed by the microprocessor.

The module 16 derives the position parameters x, y, z provided by the GPS receiver 13 to estimate the coordinates v ^" _{χ /} V, V _z of the speed vector V of the aircraft 10 in the same frame of reference, as well as the radius of instantaneous turn R of the aircraft 10 in the horizontal plane xOy. Two successive GPS measurements make it possible to estimate the speed vector V, and three successive measurements make it possible to estimate the turning radius R.

The module 17 ensures on the one hand the shaping of the cooperation messages broadcast by the radio transmitter / receiver 20, and on the other hand the decoding of the cooperation messages received from other aircraft 10 ′. Each cooperation message corresponds to a data block, whose size is for example 90 bits. An example of bit distribution in such a block is given in Table I.

Table I

In Table 1, the first six lines correspond to the instantaneous position and speed x, y, z, V _χ , V, V _z of the aircraft. The size T of the aircraft is an indication which can take four values and represents the actual size of the aircraft (for example proportional to its wingspan). The checksum (CRC) consists of three redundancy bits allowing the processing module 17 to detect possible transmission errors in a cooperation message received.

Given the difficulty of obtaining a frequency band for a communication channel, the protocol applied by the radio transmitter / receiver 20 preferably uses a common frequency channel to be shared between all the participants.

The protocol used for communication is of the time division multiple access (TDMA) type, where each aircraft transmits on a common carrier frequency. Channel optimization can be achieved by an appropriate protocol of the ALOHA type, according to which the different participants transmit in turn over fixed durations, synchronized by GPS time. Such a protocol is described in French patent 2,708,124 and its American counterpart 5,544,075 incorporated here by reference. The frequency channel is divided into reproducible time periods T _c , each period comprising a number N _c of evenly spaced time slots. Access to a time slot for transmission is done by locating free time slots during a listening period of at least T _c seconds, then by random choice of a slot from among the slots identified as being free. This method comprises a procedure for accessing the channel (listening then choosing a free track), a period of occupation of the chosen track, and a procedure for releasing the track.

To optimize the transmission time, it is useful to adapt the time periods T _c , the number of slots N _c and the data format to the present application. The adaptation of the protocol to the data to be transmitted can be as follows: a period T = 1 second is chosen in order to allow the positioning information deduced from the GPS signals to be sufficiently renewed; the number of time slots is N _c = 100 which, for the period T _c = 1 second, leaves a duration of 0.01 seconds for the transmission of the useful data. This number Nc is thus judiciously chosen to be greater than the numbers of VFR aircraft that can be encountered in the radio coverage area of the transmitter / receiver 20 in extreme cases, for example during glider competitions.

Preferably, for a transmission speed of 9600 bauds (typical value of current commercial modems which, in VHF, respect the authorized bandwidth of rl2.5 kHz), the maximum size of a data block will therefore be 96 bits by aircraft.

With this baud rate of 9600 baud, if channel occupancy is optimized, by allocating a 0.01 second slot to each aircraft, the 90-bit block in table I can be transmitted in 9.375 ms, which leaves a free interval of 625 us between consecutive messages to allow transmitters / receivers 20 to pass from transmission to reception, as well as to be able to insert, according to the method of French patent 2,708,124, listening tracks in the occupied tracks.

The radio transmitter / receiver 20 picks up the cooperation messages broadcast by the aircraft 10 'located within radio range of the aircraft 10 (typically a few kilometers), and extracts the position information x', y ', z' from these aircraft 10 ', their speed information V _χ , V _V , V _Z and their actual size indications T. This information, as well as that from the GPS receiver 13 and the bypass module 16 are processed by the analysis module 18 for assess the risk of collision. This analysis can be in accordance with the procedure represented in FIG. 3, which is executed at successive analysis instants t separated by a period T _c (t _{p + 1} = t + T _C ) if the number NA of cooperation messages received from other aircraft 10 'over the last period T _c is greater than 0.

For each aircraft 10, a fixed elementary protection volume is defined relative to the aircraft. This volume must have dimensions compatible with the positioning accuracy of the GPS, namely a few tens of meters. As illustrated in FIG. 4, this elementary protection volume Pr can be in the form of a rectangular parallelepiped, of length L in the longitudinal direction of the aircraft 10, of width 1 ^ according to the wingspan of the aircraft 10, and of height L. For example, we can take L _a = 200 m (preferential protection in the direction of movement), 1 ^ = 100 m (chosen with respect to the relative accuracy of the GPS), and L_ = 50 m (the speed of approach speed is a priori lower in the vertical direction)

From each analysis instant t, the module

18 defines a period of analysis of duration D. Advantageously, this duration D is a function of the instantaneous turning radius R and of the speed V, of the aircraft 10

in the horizontal plane xOy, i.e.

_*

In the example shown in Figure 3 (step

40), the duration D of the analysis period is an increasing function of the instantaneous turning radius R provided by the bypass module 16, namely the minimum between a reference duration D _maχ (or maximum notice period) and

, 2πR 2πR a duration equal to a. This last duration is equal

^V hv _h at the time necessary for the aircraft 10 to make a complete revolution on itself, seen in the horizontal plane, if it maintains its instantaneous speed and turning radius. Limiting the duration D to this time (or to a time proportional to this) makes it possible to adapt the amount of information that will be delivered to the pilot to the instantaneous trajectories typical of all aircraft flying in VFR (including the ascending spiral gliders).

In step 41 of the analysis procedure, the module 18 subdivides the analysis period [t, t + D] into a series of N consecutive time intervals. Each of these

time intervals have a duration δ = ^L a, the number N being

D the integer equal to or immediately greater than the ratio -. δ

Then, for each of the time intervals n = 0 to n = N-1, the module 18 determines a protection volume

Pr (n) on the basis of different possible future positions of the aircraft 10 deduced from the trajectory parameters x, y, z, V _χ , V _y , V _z , R, and examines whether other aircraft are likely to penetrate in this volume in the time interval considered. In the example shown in Figure 3, these operations are performed in a loop indexed by the integer n (initialized by n = 0 in step 42, and incremented by one unit in step 43 after execution of these operations if n <Nl in test 44).

The protection volume Pr (n) is defined in step

45 from the elementary volume Pr of FIG. 4. The construction of this protection volume Pr (n) is for example in accordance with the procedure below, illustrated by FIGS. 5 to 7.

Viewed in projection on a horizontal plane (FIG. 6), the possible future positions, _ (n) of the aircraft 10 taken into account to determine the volume of protection Pr (n) are comprised on the one hand by the half-line Δ defined by the position x, y, z and the speed vector V determined from the last GPS measurements and on the other hand the convex side of the arc of circle A defined by the position x, y, z, the speed vector V and the instantaneous turning radius R provided by the module 16. In projection in this horizontal plane, we take into account a number 1 + 1 (n) of possible positions M _{l 0} (n) for the time interval n, respectively associated with velocity vectors V. _n (n). The number I (n) depends on the relative values of n.δ, R, V _h , L _a , and 1 ^. The position M _{χ 0} (n) and the speed vector V, ₀ (n) are calculated, for O≤i≤I (n), as being those that the aircraft 10 would have at time t + n.δ if he maintained

its horizontal speed V _h = 'V _{i (0} (n) | on a trajectory of

R. I (n) constant radius of curvature equal to.

1

Viewed in projection on a vertical plane, the possible positions M (n) of the aircraft for the time interval n are between, on the one hand, the half-line Λ 'defined by the position x, y, z and the instantaneous speed vector V deduced from the GPS measurements and on the other hand the half-line Δ "defined by the position x, y, z and by the horizontal direction (figure 5). Each of the J (r.) points, _, (n), for l≤j≤J (n) (the number J (n) depends on the relative values of n.δ, V _z , L _a , and L _c ), is deduced from the point

M, ₀ (n) assuming that the vertical component of the associated velocity vector V (n) is constant from t _p to VJ t -'- n.δ and equal to, the horizontal component of

PJ (n) _: (n) being V _{χ 0} (n).

By positioning the elementary protection volume Pr with respect to the possible future position M ₁ (n), and by orienting this elementary volume along the associated speed vector (n), an elementary volume denoted Pr _χ (n) is obtained. The protection volume Pr (n) determined in step 45 for the time interval n corresponds to the union of these elementary volumes Pr ₁ (n) for O≤i≤I (n) and

0 <<J (n). This volume Pr (n) has approximately the shape shown in FIG. 7.

After having thus defined the protection volume Pr (n) in step 45, the analysis module 18 examines whether one of the aircraft 10 ′ from which a cooperation message has been received is likely to enter this volume of protection Pr (n) during the time interval n. In the example shown, this is done in a loop whose iterations are controlled by an index k designating the cooperation messages received or, equivalently, the aircraft having broadcast these messages (initialized by k = l in step 46 and incremented by one in step 47 at the end of the iteration). Each cooperation message received, corresponding to an aircraft k, associates a bit b (k) indicating whether this aircraft has been considered to represent a risk of collision during the analysis carried out from time l _Ω . Before proceeding with this analysis, all b ts b (k) are linked to 0. The number SIN, linked to 0, indicates the number of aircraft that have been considered to represent a risk of collision.

If the index k is less than or equal to the number NA of aircraft detected (test 48), and if the aircraft k has not already been identified as representing a risk of collision (b (k) = 0 during the test 49), the analysis module 18 extrapolates the trajectory of the aircraft k over the time interval n in step 50. It therefore determines the segment ^s _] < ⁿ ) ^< J ^ue will describe the aircraft k at during the time interval n if it maintains its speed vector V, the coordinates of which are provided by the processing module 17, as well as its instantaneous position x ', y', z 'also provided by the processing module 17 This segment S _k (n) ends at the two points

of coordinates + (n + l) .δ.V in the coordinate system

Cartesian common to aircraft.

In step 51, the risk of collision during the time interval n is estimated by examining whether at least part of the segment S _k (n) is inside the protection volume Pr (n). The fact of having defined the protection volume Pr (n) as a union of elementary parallelepipedal protection volumes in step 45 greatly facilitates the verification made in step 51 since it is very easy to determine whether l intersection between a segment and a rectangular parallelepiped is empty or not.

If step 51 reveals a risk of collision (non-empty intersection), module 18 calculates, in step 52, the azimuth angle φ and the site angle α corresponding to the direction in which the aircraft k possibly conflicting is visible from the aircraft 10 at time t _β . These angles é, α are simply determined by changing the coordinate system from the coordinates x, y, z and x ', y', z 'of the two aircraft.

In step 52, the module 18 also evaluates the apparent size TA of the other aircraft k from the

T ratio between the actual size T of the aircraft k,

obtained by module 17 in the corresponding cooperation message, and the distance Dιst = - '(x'-x) ² + (y'-y) ² + (z'-z) ² between the two aircraft.

In step 53, the analysis module 18 informs the man-machine interface 21 of the device that it is necessary to produce a signaling message indicating: () that a time n.δ remains to elapse before the possible collision; (n) the azimuth and site angles φ, α calculated in step 52; and (m) the apparent size TA calculated in step 52. The module 18 changes the value of bit b (k), and increases the number NAS in step 54 by one. If the number NAS is equal to number of aircraft NA, then all the aircraft for which a cooperation message has been received have already been the subject of a signaling message, so that the analysis carried out from time t is completed.

The iteration k of the loop ends with the incrementation of step 47 sb (k) = l in step 49 (aircraft already signaled), if S _k (n) nPr (n) = 0 at step 51

(collision unlikely) or if NAS <NA in step 55. When all the aircraft have been reviewed for the time interval n (k> NA in step 48), the analysis module 18 goes to step 44 to study the next time interval n, or to complete the analysis started from time t P. The human-machine interface (FIG. 2) includes a voice synthesis module 22 receiving the indications provided by the analysis module 18 in step 53. This module 22, of a constitution known per se, develops the voice signaling messages , and controls a loudspeaker or an earpiece 23 so that these voice messages are issued to the pilot.

The man-machine interface 21 also comprises a module 25 for adjusting parameters allowing the pilot, using a device such as a keyboard 26, to choose the value of certain parameters of the tracking algorithms and / or evaluation of collision risks executed by the computer 15.

In particular, it is interesting to be able to choose the value of the maximum notice period D (used in step 40). The assistance device can then deliver to the pilot more or less information, by exploring a more or less large area in front of the aircraft, according to the pilot's experience or the average reaction time which he considers to have or of the current flight phase (takeoff, cruise, approach ...).

It should be noted that the collision risk analysis procedure explained above with reference to FIGS. 3 to 7 is only one example of such a procedure that can be implemented in a device according to the invention. Different variants would be possible at different stages of the procedure.

For example, the extrapolation of the trajectory of the other aircraft in step 50 could consist in determining not a segment calculated by extending the speed vector of the other aircraft, but a volume calculated taking into account a possible variation. of the speed vector of the other aircraft within a certain range. This would however increase the amount of computation required. It is conceivable that different types of collision risk analysis are used in different aircraft, with a relatively simple analysis for inexpensive versions of the device and more sophisticated analyzes in other versions. It is also conceivable that different types of analysis are provided in the same device, and can be selected by the pilot using the unit 25 of the human interface. machine 21.

It is essentially at the level of the dissemination of cooperation messages that a certain uniformity must exist between the different VFR aircraft, so that these cooperation messages are clearly understood by everyone.

The fact that the device incorporates a GPS receiver 13 and a radio transmitter / receiver 20 makes it advantageously perform certain other functions. Thus, if the aircraft 10 is equipped with a navigation aid system 30, the positioning data x, y, z from the GPS receiver 13, and possibly the speed or curvature data ^V _X ^V _V V _Z , R produced by the bypass module 16 can be supplied to this system 30 so that it can process them.

The positioning data x, y, z regularly delivered by the GPS receiver 13 can also be supplied to a recorder 31 comprising a certain number of memory locations managed in first in / first out (FIFO) mode, so as to store a number of aircraft positions estimated up to the current time using GPS measurements. The recorder

31 is associated with a shock sensor 32 such as an accelerometer. In the event of an impact, the data stored in the recorder 31 are frozen. The recorder 31 thus plays the role of a black box making it possible to retrace the trajectory of the aircraft before the impact.

The positioning data x, y, z can also be supplied to a unit 33 for controlling a distress beacon. This unit 33 controls the radio transmitter / receiver 20, in response to a shock detected by the accelerometer.

32 or in response to the actuation by the pilot of a manual control member 34, so that a distress message, incorporating the latest data x, y, z, is transmitted, for example, on the frequency 121.5 MHz. The fact that this distress message incorporates the last position of the aircraft evaluated by the GPS receiver 13 facilitates much the location of the aircraft in difficulty, compared to conventional distress beacons which are usually identified by direction finding.

Claims

1. Visual flight piloting assistance device, to be installed on board an aircraft, comprising:

- measuring means (13,16) for estimating at least the instantaneous position and speed vector of

The aircraft;

a radio transmitter / receiver (20) for broadcasting cooperation messages containing parameters (x, y, z, V _χ , V _v , V _z ) representing at least the estimated instantaneous position and speed vector of the aircraft ( 10), and to receive similar cooperation messages broadcast from other aircraft (10 ');

- Means (18) for analyzing cooperation messages received by the radio transmitter / receiver and data from the measurement means, to identify possible risks of collision with other aircraft; and

a man-machine interface (21) for signaling to the pilot of the aircraft the possible risks of collision identified by the analysis means, characterized in that the analysis means (18) are arranged to carry out the following operations: successive moments of analysis:

- subdivide an analysis period, starting at the current analysis instant (t), into a series of consecutive time intervals;

- for each of these time intervals, determine a protection volume (Pr (n)) on the basis of different possible future positions (M (n)) of the aircraft deduced from the data from the measurement means (13,16 );

- extrapolate the trajectory of each other aircraft, from which a cooperation message is received, on the basis of the parameters contained in this cooperation message, so as to estimate possible positions of this other aircraft during the time intervals of the series ; and - s' ⁱ l is met a condition that a pos ⁱ t ⁱ on can be estimated from another aircraft in one of the series of time ⁱ ntervalles is located in the protective volume determined for said time interval , controlling the man-machine interface (21) so that n ⁱ t ⁱ dél vré the pilot a ⁱ n ⁱ signaling message as the d ⁱ rection is located in said other aircraft at the instant of current analysis.

2. D ⁱ spos ⁱ t ⁱ f according to claim 1, wherein the signaling message further indicates the time (n.δ) remaining to elapse until the first of the time intervals of the analysis period for which said condition is met.

3. D ⁱ spos ⁱ tif according to any one of the res ⁱ cat ⁱ ons preceding, in which each message of cooperation ⁱ on d ⁱ ffused by the transmitter / receiver (20) includes a ⁱ nd ⁱ cat ⁱ on of size real of the aircraft (T), and wherein each signaling message relating to another aircraft, from which a co-operation message is received, ⁱ nclut an indication of apparent size of said at ^t re aircraft (TA) determined on the basic indicating your actual lle ⁱ included in the received message of cooperation and the distance (Dist) between the two aircraft DEDU ⁱ te the estimated position by the measurement means and the pos ⁱ t ⁱ on s other aircraft included in the cooperation message received.

4. D ⁱ ⁱ t ⁱ f dev ce according to any one of the preceding sells ⁱ cat ⁱ ons, wherein the man-mach ⁱ interface ⁽²¹⁾ comprises means (22) for outputting messages from s ⁱ SIGNS AND SIGNALS under form of voice messages.

5. D ⁱ spos ⁱ t ⁱ f according to claims 2, 3 and 4, wherein each voice signaling message relating to another aircraft is composed of an indication of the nature of the message, said time remaining (n.δ), the direction in which said other aircraft is located, expressed by an azimuth angle (φ) and a site angle (α), and the indication of apparent size (TA).

6. Device according to any one of the preceding claims, in which the measuring means comprise a receiver (13) of positioning reference signals coming from a constellation of satellites.

7. Device according to any one of the preceding claims, in which the radio transmitter / receiver (20) is arranged to operate according to a time-division multiple access protocol on a common carrier frequency, the cooperation message being transmitted. in a time slot not occupied by a cooperation message from another aircraft.

8. Device according to any one of the preceding claims, in which the measuring means (16) are arranged to estimate an instantaneous turning radius (R) of the aircraft in a horizontal plane, and in which the possible future positions of the aircraft (M (n)), on the basis of which the analysis means (18) determine the protection volumes (Pr (n)), depend on the instantaneous turning radius estimated by the measuring means.

9. Device according to claim 8, in which the duration (D) of the analysis period is chosen as an increasing function of the instantaneous turning radius (R) estimated by the measuring means (16).

10. Device according to claim 9, in which the duration (D) of the analysis period is chosen as the minimum between a reference duration (D „„) and a duration proportional to the ratio between the instantaneous turning radius (R) estimated by the measuring means and the modulus (V _h ) of the projection on the horizontal plane of the instantaneous speed vector (V) estimated by the measuring means.

11. Device according to claim 10, in which the reference duration (D _j . ^) Is adjustable by means of the man-machine interface (21).

12. Device according to any one of claims 8 to 11, in which, viewed in projection on a horizontal plane, the possible future positions of the aircraft (M (n)), on the basis of which the analysis means ( 18) determine the protection volumes (Pr (n)), are between the half-line (Δ) defined by the instantaneous position and speed vector estimated by the measurement means (13,16) and the convex side of l arc of a circle (A) defined by the instantaneous position, speed vector and turning radius estimated by the measuring means.

13. Device according to claim 12, in which, viewed in projection on a vertical plane, the possible future positions of the aircraft (M, _ (n)), on the basis of which the analysis means (18) determine the protection volumes (Pr (n)), are between the half-line (Δ ') defined by the position and the instantaneous speed vector estimated by the measurement means and the half-line (Δ ") defined by the instantaneous position estimated by the means of measurement and by the horizontal direction.

14. Device according to any one of the preceding claims, in which the duration (D) of the analysis period is at most equal to a reference duration (D _j - ^ _x ) adjustable by means of the man interface. machine (21).

15. Device according to any one of the preceding claims, in which the radio transmitter / receiver (20) is arranged to broadcast a distress signal, including the position of the aircraft estimated by the measuring means (13), response to manual pilot control and / or automatic collision detection.

16. Device according to any one of the preceding claims, in which at least some of the data from the measurement means (13) are also supplied to a navigation aid system (30).

17. Device according to any one of the preceding claims, further comprising means (31) for recording a number of positions of the aircraft estimated by the measuring means (13) up to the current time. , the record being frozen in response to an automatic collision detection.